AT&T MERLIN LEGEND Release 2.0 Equipment And Operations Manual page 47

Introduction
Since the outside trunks are pooled, outside numbers are not associated with
individual telephones. When a pool is assigned to a line button during system
programming, it is called a pool button. Users request specific trunk pools by
dialing the trunk pool number (870-879) for the pool or by pressing a pool
button, which gives one-touch access to a group of trunks.
Telephone # 1
Figure 1-5. Hybrid/PBX Mode
Outside calls are normally answered by a system operator and transferred to
individual system users.
Telephone # 2
Telephone # 3 Telephone # 4
Modes of Operation
1-19